The present invention relates to a skimming apparatus comprising a movable scraper arm for a glass tank, wherein said scraper arm traverses across the surface of the molten glass mass to produce a portion thereof free from contamination.
The surface of a molten glass mass (glass melt) in a processing tank frequently shows non-homogeneities and impurities which aggravate or even prevent the production of high quality glass articles. These defects are due to the fact that, on the one hand, air bubbles may enter the melt during the withdrawal of glass lumps, and, on the other hand, in the case of specific types of glass the upper layer of the melt assumes a composition different from that of the major part of the molten mass, by evaporation of volatile components.
Laid-open German patent application Ser. No. 2,711,811 discloses a feeder apparatus wherein, in order to obtain a homogeneous surface layer free from contaminants, the surface of the glass bath or mass is scraped off by a skimmer or scraper arm before a lump is taken out. The lateral edge of the feeder is aligned with the surface of the molten glass mass, and the skimming arm pushes the surface layer of the molten glass across this edge.
In the conventional feeder apparatus, the skimmer or scraper arm is mounted to a rotatable shaft being disposed adjacent to the feeder. This results in the drawback that the rotating skimmer arm requires much installation space. Particularly when the glass lumps are withdrawn manually, the rotating skimmer arm is dangerous to the operators, too. A particularly serious disadvantage of the conventional apparatus resides in the fact that the skimmer arm is not adapted to be immersed into glass melt to a sufficient depth, because this arm rotates above the wall defining the feeder. A skimmer or scraper arm which rotates above the surface of the glass melt exclusively without traversing the wall, however, would not be adapted to adequately remove the upper layer of the molten glass mass from the glass tank. Still further, the conventional skimmer arm, owing to its vertically positioned axis, cannot be operated through the laterally positioned openings which are anyhow present in feeders for the removal of glass lumps.